Various electric lawn mowers and other types of electric working machines have been known, among which are a battery-powered lawn mower disclosed in Japanese Patent No. 2,837,960, an electric working machine disclosed in Japanese Patent Laid-open Publication No. HEI-10-191750 and a battery-powered electric working machine disclosed in Japanese Patent Laid-open Publication No. HEI-9-65752.
The battery-powered lawn mower disclosed in the No. 2,837,960 patent includes an electric motor mounted on a vehicle chassis and covered with a housing and a battery pack accommodated in the housing, in which a power on/off key is removably inserted in an upper portion of the housing rearwardly of the battery pack. The electric working machine disclosed in the No. HEI-10-191750 publication includes a motor switch provided on a rear end portion of a cutter housing cover, where the motor switch is operated by turning of a power on/off key inserted in the switch.
Generally, in the electric lawn mowers of the type where grass clippings are delivered, through the scroll portion, to a rear portion of the machine body to be ultimately collected into the grass bag, there arises a need to clean the scroll portion from time to time because the grass clippings tend to adhere to the surface of the scroll portion. For cleaning the scroll portion in the above-discussed battery-powered lawn mower, where the power on/off key is provided in an upper rear portion thereof, it is necessary for a human operator to move over to a rear portion of the machine body so as to pull the power on/off key out of the housing and then move to a side of the machine body so as to lay the machine body down sideways for access to the scroll portion. Similarly, for cleaning the scroll portion in the above-discussed electric working machine, where the motor switch is provided on a rear end portion of the cutter housing cover, it is necessary for a human operator to move over to a rear portion of the machine body so as to pull the power on/off key out of the motor switch and then move to a side of the machine body so as to lay the machine body down sideways for access to the scroll portion. Namely, for both the known battery-powered lawn mower and the known electric working machine, it is desirable that the power on/off key be inserted in such a position of the lawn mower or working machine as to allow the human operator to easily clean the scroll portion.
Further, in the electric working machine disclosed in the No. HEI-10-1917150 publication, the motor switch is provided on a support plate having a charging connector mounted thereon, and the motor switch and charging connector are exposed for external access through an opening formed in the housing cover. Here, when the working machine is activated by turning the power on/off key inserted in the motor switch, a manipulating portion of the power on/off key overlaps or covers the charging connector to prevent a recharger from being mistakenly connected to the working machine during operation of the working machine. Further in the battery-powered electric working machine disclosed in the No. HEI-9-65752 publication, a charging socket and interlocking switch for turning on/off a power supply circuit are both provided on a charging operation panel, and a cover member is also provided on the charging operation panel for sliding movement between the socket and the interlocking switch. Here, the cover member has a projection to cause the interlocking switch to be turned on as the cover member covers the socket but turned off as the cover member uncovers the socket.
However, although the electric working machine disclosed in the No. HEI-10-191750 publication has not only the primary safety function performed by the motor switch and power on/off key but also the extra function of preventing the recharger from being mistakenly connected to the working machine during operation of the working machine, it can not perform these two safety functions by means of a single simplified structure; namely, the primary safety function and the extra function of preventing mis-connection of the recharger have to be performed by separate elements. Further, because the projection is integrally formed on the cover member in the battery-powered electric working machine in the No. HEI-9-65752 publication, the working machine is activatable only via a key switch mechanism while sacrificing part of the necessary safety function; that is, the safety function of a key switch mechanism and the safety function relating to connection with the recharger can not be performed simultaneously, and thus one cannot help saying that the disclosed electric working machine is unsatisfactory from the viewpoint of safety.